As oil and gas exploration has required the drilling of wells to greater and greater depths, the use of metal-to-metal seals has become more desirable and in some cases essential. Previous designs for metal-to-metal seals have typically required an activation means of one form or another, resulting in increased complexity and increased difficulty in deploying the seals. Those designs which did not require additional activation means usually depended upon an initial interference between the seal element and the surfaces to be sealed against. These interference type seals could be damaged during the initial installation procedure which required the seal element to be "stabbed" into position. Also, these interference type metal-to-metal seals were made of a relatively soft metal to allow the seal element to "flow" and fill in scratched or damaged surfaces. Since the seal element was constructed from relatively soft metal, it would quickly lose its initial interference with the surfaces sealed against and commence leaking.
The present invention relates to an interference type metal-to-metal seal which uses low interference between the seal element and the surfaces sealed against in conjunction with various support elements to maintain this initial sealed condition. In the E. E. Castor U.S. Pat. No. 3,378,269, a metal-to-metal seal of a generally U shape is disclosed which establishes an initial seal by interference between the seal element and the surfaces sealed against.
The C. F. Boehm, Jr. U.S. Pat. No. 4,665,979 discloses a metal-to-metal seal for use in the annulus between a casing hanger and wellhead housing. The seal is U shaped and has no initial sealing interference when installed. An energizer ring is forced between the legs of the U shaped member to urge the legs into sealing engagement with the hanger and housing. The energizer ring has ports which prevent excessive fluid pressure during energization of the seal. The S. D. Gullion U.S. Pat. No. 4,742,874 discloses a similar type of seal in which a U shaped seal of unequal length legs is urged into sealing engagement by wedge rings.
The W. M. Taylor U.S. Pat. No. 4,749,047 discloses an annular wellhead seal which is activated by inserting the seal into the annulus to be sealed and forging the upper rim of the hanger outward with pressure into sealing engagement with the seal.
The J. D. Smith et al. U.S. Pat. No. 4,766,956 discloses another annular wellhead seal which uses upper and lower U shaped seal legs with a curved tip. The curved tips are moved into engagement with the seal bores by mechanical activation means.